In an electromagnetically driven fluid pump with a diaphragm, a diaphragm made of, for example, a rubber is fixed at both ends of an oscillator having magnets fixed thereto, an outer periphery of the diaphragm is fixed to a frame and a pump casing, electromagnets are arranged so as to face the magnets of the oscillator, and the electromagnets are enclosed with a casing. A passage of a fluid is formed outside the diaphragm with the casing, and the oscillator is vibrated synchronously with a change in polarity of the electromagnets resulting from a change in polarity of ac power to be applied to the electromagnets, thereby vibrating the diaphragm and repeating suction and discharging of a fluid such as a liquid or gas.
A diaphragm is fixed to an oscillator as shown, for example, in FIG. 10. Namely, a fitting screw portion 107 is fixed at an end of a supporting portion 103 of an oscillator 102, to which a permanent magnet 110 is fixed. A through-hole 108 is formed at the center of the diaphragm 104 made of a rubber member or the like, and the diaphragm is sandwiched with an inner center plate 105 having a protruded portion fitting to the through-hole 108 and an outer center plate 106. The fitting screw portion 107 of the oscillator 102 is inserted in a through-hole 109 disposed at the center of the inner and outer center plates 105 and 106 and a nut 113 is fastened from the outside via a washer 112, thereby fixing the diaphragm (See, for example, JP 2003-35266 A). These inner and outer center plates 105 and 106 are made of metal or plastic, and are sandwiching the diaphragm 104 with the surfaces of the center plates being wider than that of the washer 112 and than the end surface of the supporting portion 103, thus fixing the diaphragm 104 to the oscillator 102. Thereby, the diaphragm 104 is not pressed directly onto the peripheral edge of the washer 112 or the peripheral edge at the end of the supporting portion 103, and wearing of the diaphragm 104 is prevented.
In addition, for example, a simplified structure as shown in FIG. 11(a) is used on a small size electromagnetically driven fluid pump. In this structure, an end portion 114 of a supporting portion 103 is formed in the same size and shape as those of a center plate 106, and an internal thread hole 115 is provided on the end portion 114 instead of the fitting screw portion 107. A diaphragm 104 and the center plate 106 are disposed in this order, and a screw 116 is screwed in the internal thread hole 115 from the center plate 106 side, and thereby the diaphragm 104 is sandwiched and is fixed between the center plate 106 and the end portion 114 of the supporting portion 103.